Top-down functions (e.g., attention and working memory) go hand-in-hand with consciousness. Yet we know more about the former, because it is hard to define consciousness in most contexts. There is, however, a way in. General anesthesia (GA) provides transition through different stages of consciousness. We aim to determine which aspects of cortical processing are critical for these changes by using a surgical anesthetic, propofol, in monkeys. Propofol increases cortical-wide delta oscillations and alpha in frontal cortex. One hypothesis posits that the increased frontal alpha disrupts top-down cortical feedback from frontal cortex. Another points to the widespread delta oscillations that, unlike sleep, are decoupled across cortex. This could fragment long-range communication across cortex or, as some suggest, loss of consciousness (LOC) could be due to frontal-parietal cortex disconnectivity per se. The thalamus is likely to play a major role. Mounting evidence suggests it controls top-down cortical processing, perhaps by modulating cortical oscillations. Abnormal thalamic oscillations could entrain different cortical areas or the changed dynamics could be largely a cortical phenomenon. Previous primate studies of GA lack the combination of wide scope and single-neuron precision to directly test these hypotheses. We will use chronic intracranial multiple electrodes in monkeys to record simultaneously from a wide range of critical brain structures (prefrontal cortex, posterior parietal cortex, auditory cortex, and thalamus). We will also test if thalamic stimulation can restore consciousness and wakeful cortical dynamics.